Chemical vapor deposition (CVD) processes are commonly used for depositing a thin film on a substrate. A CVD processing system typically includes a vacuum chamber into which the substrate is placed. A gaseous precursor is introduced into the chamber and the thin film is formed as a result of reactions or decomposition of the gaseous precursor at the surface of the substrate. A carrier gas may be used to carry the precursor into the process chamber. Devices for vaporizing liquid or solid deposition precursor materials are known in the art. One such device used to vaporize a liquid precursor is commonly referred to as a "bubbler," an example of which is schematically shown in FIG. 1. Bubblers may be employed in CVD systems using a liquid precursor such as DMAH, TDMAT, TEOS, etc. The bubbler includes a container 12 having a quantity of liquid precursor 14 therein. A carrier gas is introduced from a gas source (not shown) into the container 12 through a conduit or sparger pipe 16 having an opening 18 below the surface of the liquid precursor 14 in the container 12. The opening 18 is usually at a point near the bottom of the container 12. Upon being introduced into the liquid precursor 14, the carrier gas forms discrete bubbles 20, after exiting the liquid precursor 14, which rise to the surface. Each bubble 20 will contain a quantity of the precursor in vapor form. The carrier gas containing the deposition precursor vapor is collected in the bubbler in the space 22 above the level of the liquid precursor 14, and is delivered from the bubbler through an outlet pipe 24 to the process chamber (not shown). The pipes 16 and 24 typically have a diameter of 1/4 inch.
Due to its physical and chemical properties, the gaseous deposition precursor material may be prematurely deposited on the inner walls of the delivery piping. Such deposition of material on the piping walls may cause clogging, contamination and have other harmful effects on the gas delivery and deposition process. As a result, the portion of the delivery system through which the vaporized deposition material flows requires cleaning from time to time. Methods for removing material deposited on the piping walls have been developed. Such methods include the application of a gas or liquid to the piping walls to etch or dissolve away the accumulated material. While the gas delivery systems having cleaning subsystems have been utilized, it would be desirable to increase the efficiency of the cleaning delivery subsystem so improve the overall process throughput.